Located North West of Xoda Island is the Xoda Island lighthouse. (YES I know it's not a cube room but it still counts)

Each floor is featured here.

Ground Floor: Power and emergency generator room.
First Floor: Storage Room (Food Supplies and Replacement parts)
Second Floor: Kitchen (Making and Baking)
Third Floor: Sitting Room (Relaxation)
Fourth Floor: Bedroom and Bathroom (Sleeping)
Fifth Floor: Communications Room (Radio and Radar)
Sixth Floor: Light Room (The Top)

Credit for this artwork must go to  Gehirnlie who did a fantastic job.